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Physiology of sleep and dreaming. The sleep cycle Dreaming Why do we sleep?. The sleep cycle. Electronic recording: EEG, EOG, EMG EEG patterns divide sleep into four stages: 1: a waves, 8 - 12 Hz, low amplitude, moderate frequency, similar to drowsy wakefulness

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physiology of sleep and dreaming

Physiology of sleep and dreaming

The sleep cycle

Dreaming

Why do we sleep?

the sleep cycle
The sleep cycle
  • Electronic recording: EEG, EOG, EMG
  • EEG patterns divide sleep into four stages:
    • 1: a waves, 8 - 12 Hz, low amplitude, moderate frequency, similar to drowsy wakefulness
    • 2: slower frequency, higher amplitude, plus
      • K complexes
      • Sleep spindles
    • 3: d waves appear, 1-2 Hz, large amplitude
    • 4: Dominated by d waves
rem sleep phenomena
REM sleep phenomena
  • Stage 1 EEG: Paradoxical sleep
  • EOG (and corneal bulge) show frequent eye movements, as if scanning a visual field.
  • EMG shows loss of muscle tonus due to downward inhibition of a motor neurons, although muscles moving hands and feet may twitch.
  • Many brain structures function as if awake.
more rem phenomena
More REM phenomena
  • SNS is partially activated: Increases blood pressure, respiration, and heart rate.
  • Genital erection or partial erection: Postage stamp test.
  • Narrative dreaming
    • CBF is high to visual cortex, low to inferior frontal cortex (Madsen, 1991)
    • Eye movements match dream events
    • One EEG waveform is unique to REM and wakeful scanning
dream research
Dream research
  • External stimuli may be incorporated into a dream.
  • Dream events happen in real time.
  • Everyone dreams; recall depends on when in the sleep cycle you awaken.
  • Genital response is independent of dream content.
  • Sleep-walking and talking are non-REM.
interpretation of dreams
Interpretation of dreams
  • Manifest content is symbolic of latent desires (Freud)
  • Activation-synthesis theory: cf. incorporation of external events into dreams.
  • Lucid dreams: Have you had one?
why do we sleep
Why do we sleep?
  • Restoration, recuperation or repair
    • Waking life disrupts homeostasis
  • Protection with the circadian cycle
  • Circadian synthesis
who sleeps
Who sleeps?
  • Mammals and birds
    • Opossums, sloths, bats: 19-20 hours daily
    • Cats, dogs, rodents: 12-15 hours daily
    • Ruminant herbivores: 2-3 hours daily
  • Reptiles, amphibians, fish, and insects have cycles of inactivity
  • Note that sleep time does not correlate with waking activity levels, but does relate to waking vulnerability.
two interesting variations on sleep
Two interesting variations on sleep
  • Cetaceans
    • Indus dolphin
    • Bottlenose dolphin and porpoise
  • Flocking birds
circadian rhythms
Circadian rhythms
  • Zeitgebers and the SCN
  • Free-running rhythms and the 25-hour period
  • Sleep deprivation within a circadian cycle is followed by less sleep, not more
  • Internal desynchronization: free-running body temperature cycle and sleep-wake cycle may desynchronize.
resynchronization
Resynchronization
  • Jet lag and shift work
  • Phase shift: Delay is better than advance
    • Morning melatonin phase-delays
    • Afternoon melatonin phase-advances
    • Evening melatonin is ineffective
    • Bright light exposure has the opposite effects
  • Strengthen zeitgebers like light and activity early in the new waking period
sleep deprivation
Sleep deprivation
  • Under total, voluntary sleep deprivation, sleepiness is cyclical
    • Greatest sleepiness from 3-6 a.m.
    • Waking sleepiness is countered by activity
    • Sleepiness increases only up to four days
  • Active, complex tasks are not impaired
  • Easy, boring tasks are impaired
  • Microsleep emerges
compensation for sleep deprivation
Compensation for sleep deprivation
  • Subsequent slow-wave, non-REM sleep is increased
  • Stage 3 and 4 sleep is almost completely restored
  • Involuntary sleep deprivation is stressful
    • Executive rats on a carousel apparatus died
    • Post-mortem exams showed stress symptoms
rem deprivation
REM deprivation
  • REM pressure
  • REM rebound
  • REM escape
  • Three theoretical effects
    • Mental disorder
    • Amotivational syndrome
    • Memory processing deficits
    • But tricyclic antidepressants block REM with none of these side effects.
neural control of sleep
Neural control of sleep
  • Is sleep a passive process?
    • The cerveau isole’ of Bremer (1936)
    • The encephale isole’ and the RAS
    • Partial transections leaving the RAS intact
  • Ventrolateral Preoptic Area (VPA) triggers sleepiness and slow-wave sleep
  • Warming the basal forebrain induces slow-wave sleep
  • VPA receives input from thermoreceptors
more neural control
More neural control
  • PGO waves in the EEG from implanted electrodes
  • Executive in the dorsolateral pons, called the peribrachial area.
  • Kainic acid lesions of peribrachial area reduce REM sleep
  • Carbachol, and ACh agonist, in ventral pons (medial pontine reticular formation) triggers REM phenomena.
eeg patterns
EEG patterns

b

1 a

2 k

3 d

1 sec